/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package com.googlecode.activemq.eclipse.views;

import org.eclipse.jdt.core.IClassFile;
import org.eclipse.jdt.core.ICodeAssist;
import org.eclipse.jdt.core.ICompilationUnit;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.internal.corext.util.JavaModelUtil;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.javaeditor.IClassFileEditorInput;
import org.eclipse.jdt.internal.ui.javaeditor.JavaEditor;
import org.eclipse.jdt.ui.IWorkingCopyManager;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.ui.IEditorInput;

/**
 * Helper class to convert text selections to Java elements.
 * 
 * @since 3.0
 */
class TextSelectionConverter {

	/** Empty result. */
	private static final IJavaElement[] EMPTY_RESULT = new IJavaElement[0];

	/** Prevent instance creation. */
	private TextSelectionConverter() {
	}

	/**
	 * Finds and returns the Java elements for the given editor selection.
	 * 
	 * @param editor
	 *            the Java editor
	 * @param selection
	 *            the text selection
	 * @return the Java elements for the given editor selection
	 * @throws JavaModelException
	 */
	public static IJavaElement[] codeResolve(JavaEditor editor, ITextSelection selection) throws JavaModelException {
		return codeResolve(getInput(editor), selection);
	}

	/**
	 * Finds and returns the Java element that contains the text selection in
	 * the given editor.
	 * 
	 * @param editor
	 *            the Java editor
	 * @param selection
	 *            the text selection
	 * @return the Java elements for the given editor selection
	 * @throws JavaModelException
	 */
	public static IJavaElement getElementAtOffset(JavaEditor editor, ITextSelection selection) throws JavaModelException {
		return getElementAtOffset(getInput(editor), selection);
	}

	// -------------------- Helper methods --------------------

	private static IJavaElement getInput(JavaEditor editor) {
		if (editor == null)
			return null;
		IEditorInput input = editor.getEditorInput();
		if (input instanceof IClassFileEditorInput)
			return ((IClassFileEditorInput) input).getClassFile();
		IWorkingCopyManager manager = JavaPlugin.getDefault().getWorkingCopyManager();
		return manager.getWorkingCopy(input);
	}

	private static IJavaElement[] codeResolve(IJavaElement input, ITextSelection selection) throws JavaModelException {
		if (input instanceof ICodeAssist) {
			if (input instanceof ICompilationUnit) {
				ICompilationUnit cunit = (ICompilationUnit) input;
				if (cunit.isWorkingCopy())
					JavaModelUtil.reconcile(cunit);
			}
			IJavaElement[] elements = ((ICodeAssist) input).codeSelect(selection.getOffset(), selection.getLength());
			if (elements != null && elements.length > 0)
				return elements;
		}
		return EMPTY_RESULT;
	}

	private static IJavaElement getElementAtOffset(IJavaElement input, ITextSelection selection) throws JavaModelException {
		if (input instanceof ICompilationUnit) {
			ICompilationUnit cunit = (ICompilationUnit) input;
			if (cunit.isWorkingCopy())
				JavaModelUtil.reconcile(cunit);
			IJavaElement ref = cunit.getElementAt(selection.getOffset());
			if (ref == null)
				return input;
			else
				return ref;
		} else if (input instanceof IClassFile) {
			IJavaElement ref = ((IClassFile) input).getElementAt(selection.getOffset());
			if (ref == null)
				return input;
			else
				return ref;
		}
		return null;
	}
}
